Chemical composition of human enamel and dentin. Preliminary results to determination of the effective atomic number

摘要

The theoretical or practical dosimetry involving radiation interactions in humans needs the reliableelemental composition data of body tissues. The object of this research was to obtain the characterization dentalhard tissues and to determine its effective atomic number. An analytical research of inorganic composition, from30 intact human molars, extracted for periodontal reasons, was performed by Neutron Activation Analysis(NAA), ICP/AES, Thermogravimetric (TG) and Differential Thermal Analysis (DTA). The coronal dentin andenamel were separated by two techniques: (1) - mechanically by chipping and breaking by chirurgic hammer,allowed to dry in an electric oven for 5 hours at 1600C. (2) - through by high-running round steel burs. Thesamples were thoroughly cleaned with distilled deionizer water and sent for analysis in CDTN/CNENlaboratories, Belo Horizonte, Minas Gerais, Brazil. The results showed concentrations of 11 elements measuredin dentin and enamel. The five elements of the higher concentration by neutron activation analysis and ICP/AESwere Ca, P, Na, Mg and Al. Thermogravimetric analysis of enamel showed a loss of water of hydroxyapatite to5000C. Thermogravimetric analyses of dentin showed tree temperatures at which mass loss occur. Theseprocesses are related to superficial water loss (100oC); organic decomposition and water liberation fromhydroxyapaptite (100oC to 600oC); and the beginning of hydroxyapatite decomposition (600oC to 850oC).Differences, in mineral concentration, were found between enamel and dentin, with higher concentrations inenamel. The two techniques proposed to separated dentin and enamel, no presented differences in elementsconcentration, statement that the high-running round steel burs technique didn’t affected the samples.